Do you know anything about a rainbow-like cloud-is it unusual?
Yes...but no, it's not that unusual. It's actually not a rainbow-the colored arc forms when sunlight passes through ice crystals in high clouds, bending and separating into the component colors of light. A particular type of ice crystal is required-flat, six sided 'plates'. If sunlight strikes, enter and then passes through the crystals at the right angle...then we see what's called a 'circumhorizon arc'. Such arcs require the sun to be high in the sky-conditions make such arcs most likely to be seen in the Pacific Northwest from May to August.